Photographic processing of silver halide color photographic materials basically comprises development (in the case of color reversal materials, color development is preceded by black-and-white first development), desilvering, and washing. Desilvering comprises bleaching and fixing or combined bleach-fixing (blix). The processing further includes supplementary steps, such as stabilization, prebath processing preceding each step, and stopping. In color development, an exposed silver halide is reduced by a color developing agent to form silver and halogen ions. Simultaneously, the oxidized color developing agent reacts with a coupler to form a dye. The developed silver is re-halogenated by bleaching and removed by fixing (or blix) together with undeveloped silver.
Bleaching agents which have been mainly used include red prussiate (potassium ferricyanide) and aminopolycarboxylic acid ferric salts. Potassium ferricyanide is an excellent bleaching agent exhibiting a sufficiently high rate of bleaching but releases cyanide ion on photolytic degradation causing environmental pollution. Therefore, a countermeasure should be taken to make the waste liquid completely harmless. On the other hand, aminopolycarboxylic acid ferric salts are now being used widely because of they cause less environmental pollution and they can be regenerated easily (a ferrous salt is easily oxidized to a ferric salt by contact with air). Nevertheless, if it remains in a light-sensitive material due to insufficient washing, the white background of an image shows increased stain with time. Therefore, a light-sensitive material after bleach or blix should be washed with a sufficient amount of water for a sufficient time. Also with respect to environmental conservation, even an aminopolycarboxylic acid ferric salt is not perfect (e.g., it has a high BOD or COD). Hence, a demand exists for an oxidizing agent having a rapid bleaching power without causing environmental pollution.
Hydrogen peroxide is an ideal oxidizing agent which decomposes into water and does not cause environmental pollution. Various bleaching solutions using hydrogen peroxide have hitherto been proposed. For example, the latest proposals include a bleaching solution or a bleaching method for desilvering using hydrogen peroxide under a neutral to acidic condition (pH 2 to 6) under which a dye image is not substantially formed as disclosed in JP-A-53-23633, JP-A-53-75932, and JP-A-54-1027 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), and a hydrogen peroxide bleaching solution containing an organic metal complex salt to obtain enhanced bleaching power as disclosed in JP-B-61-16067 and JP-B-61-19024 (the term "JP-B" as used herein means an "examined Japanese patent publication"). However, a hydrogen peroxide bleaching solution has a problem in that bleaching power and liquid stability are not simultaneously achieved. That is, a bleaching solution having increased stability has weak bleaching power, while stability of the hydrogen peroxide in a solution having increased bleaching power is not maintained. In addition, it is extremely difficult to accomplish desilvering within a short time of 30 seconds while maintaining liquid stability.
In order to accelerate bleaching, bleaching or bleach-fix solutions containing hydrogen peroxide together with a compound capable of forming a soluble silver salt with a silver ion under a neutral to alkaline condition have been proposed as disclosed in U.S. Pat. Nos. 4,454,224, 4,717,649, and 4,737,450. These solutions, however, still require a long time for bleaching and are not sufficient to achieve rapid bleach. Moreover, JP-A-53-75932 describes that processing with a bleaching or blix bath containing hydrogen peroxide tends to result in the formation of bubbles which results in a blister phenomenon, particularly on abrupt initiation of the bleaching reaction with silver. That is, in achieving rapid desilvering, compatibility of rapid bleaching reaction with inhibition of blister has been an important subject to consider.
Stability of hydrogen peroxide in an aqueous solution can be increased by addition of a stabilizer, such as sodium pyrophosphate and sodium stannate, as taught, e.g., in Research Disclosure, No. 11660 or W.C. Schump, Hydrogen Peroxide, pp. 515-547, Reinnold (1955), but the stability attained is still insufficient. Addition of an organic phosphonic acid to an intensifier to improve stability of hydrogen peroxide as disclosed, e.g., in JP-B-56-45131 has been proposed in carrying out intensification of a dye image using hydrogen peroxide. Decomposition of hydrogen peroxide is, in general, catalytically accelerated in the presence of a trace amount of a metal and, as a result, oxygen is released. It is therefore considered that the stability of hydrogen peroxide may be improved by addition of a certain type of sequestering agent (chelating agent). However, even when the decomposition of hydrogen peroxide is inhibited by using such a stabilizer, the formation of bubbles in the liquid on silver bleaching cannot be inhibited, and under certain processing conditions, blisters are easily formed.
Where a light-sensitive material after color development is processed with a hydrogen peroxide-containing solution having a pH of neutrality or higher (e.g., pH 8 or higher), it has turned out that intensification reaction of the dye image preferentially takes place due to a color developing agent which has been carried over by the light-sensitive material. As a result, bleaching of the image silver is retarded and, in particular, an area of low image silver amount (e.g., on a 10 mg/m.sup.2 level) is not completely bleached.
Further, bleaching by a hydrogen peroxide-containing bleaching solution is considerably inhibited when the solution is contaminated with even a trace amount of halogen ions dissolved from a light-sensitive material. In actual processing, since as halogen ions are accumulated through continuous running, desilvering insufficiency develops despite a sufficient concentration of hydrogen peroxide being present.
As stated above, many problems remain awaiting solution in using hydrogen peroxide as a practical bleaching agent.